DOCSLIB.ORG

Measurements of Some Gamma-Ray Relative Intensities and Internal

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Measurements of Some Gamma-Ray Relative Intensities and Internal Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1967 Measurements of some gamma-ray relative intensities and internal conversion coefficients using a bent-crystal monochromator Gerald Clifford Nelson Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Nuclear Commons Recommended Citation Nelson, Gerald Clifford, "Measurements of some gamma-ray relative intensities and internal conversion coefficients using a bent- crystal monochromator " (1967). Retrospective Theses and Dissertations. 3198. https://lib.dr.iastate.edu/rtd/3198 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. This dissertation has been microfihned exactly as received 6 8-596 9 NELSON, Gerald Clifford, 1940- MEASUREMENTS OF SOME GAMMA-RAY RELATIVE INTENSITIES AND INTERNAL CONVERSION COEFFICIENTS USING A BENT-CRYSTAL MONOCHROMATOR. Iowa State University, Ph,D., 1967 Physics, nuclear University Microfilms, Inc., Ann Arbor. Michigan MEASUREMENTS OF SOME GAMMA-RAY RELATIVE INTENSITIES AND INTERNAL CONVERSION COEFFICIENTS USING A BENT-CRYSTAL MONOCHROMATOR by Gerald Clifford Nelson A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF PHILOSOPHY Major Subject: Physics Approved: Signature was redacted for privacy. In Charge of Major Work Signature was redacted for privacy. Department Signature was redacted for privacy. Iowa State University Of Science and Technology Ames, Iowa 1967 il TABLE OF CONTENTS Page ABSTRACT I. INTRODUCTION 1 A. Definition of the Internal Conversion Process 1 B. Remarks About Internal Conversion Coefficients 3 C. Experimental Methods of Measuring Internal Conversion Coefficients 6 D. Some Experimental Methods of Measuring Gamma-Ray Relative Intensities 8 II. THEORY OF THE LINEAR LEAST-SQUARES SCINTILLATION METHOD 18 III. EXPERIMENTAL EQUIPMENT AND METHODS 23 IV. MEASUREMENTS AND RESULTS 38 A. Internal Conversion Coefficients of the E2 Transitions in Yb^^O and Er^^^ 38 1. Internal conversion coefficient of the 84.3-keV transition in Yb^^^ , 38 2. Internal conversion coefficient of the 80.6-keV transition in Er^^^ 49 3. Discussion of the E2 internal conversion coefficients in Yb^^O and Er^^^ 56 B. Internal Conversion Coefficients in Hf^^^ 57 180 1. Analysis of the Hf X-ray and gamma-ray spectrum 59 2. Results and discussion 71 C. K Internal Conversion Coefficients in Gd^^^ 76 1. Analysis of the Gd^^^ X-ray and gamma-ray spectrum 76 2. Results and discussion 84 D. Relative Intensities of the 104-, 142- and 246-keV 1RA Gamma Rays in Eu 86 iii 155 Page 1. Analysis of the Eu gamma-ray spectrum 87 2. Results and discussion 90 E. Concluding Remarks 96 V. LITERATURE CITED 98 VI. ACKNOWLEDGMENTS 103 VII. APPENDIX A: EFFECTS DUE TO SOURCE WIDTH AND POSITION 104 VIII. APPENDIX B: CALCULATION OF THE EFFICIENCY OF THE NAI CRYSTAL 110 IX. APPENDIX C: DERIVATION OF THE ERRORS ASSOCIATED WITH THE LINEAR LEAST-SQUARES PROCEDURE 121 X. APPENDIX D: FLOW CHART AND REVISED COMPUTER PROGRAM 137 iv ABSTRACT The X-ray and gamma-ray relative intensities were measured, from the decay of and Sm^^^ with a bent-crystal mono- chromator and a linear least-squares computer program. The K-shell internal conversion coefficients were determined for the E2 transitions in and Er . The K-shell conversion coefficient, for the 84.3-keV transition in Yb^^^ was determined to be 1.43±0.04 while the K-shell internal conver­ sion coefficient for the 80.6-keV transition in Er was determined to be 4* + 1.72±0.06. The results for these 2 -K) transitions are five percent higher than the theoretical values for these transitions. From the relative inten- 180 sities of the transitions in Hf it was possible to deduce a value for the 93 total internal conversion coefficient for the 93.3-keV transition of cy = 4.91±0.23. Using the previous measurements of conversion electron intensi­ ties of Edwards and Boehm and the present measured gamma-ray relative inten­ sities, internal conversion coefficients for all the other transitions were obtained. The present measurements of for the 215.3-, 332.5- and 443.8- keV E2 transitions are 11 percent lower than the theoretical values, while for the 93.3-keV E2 transition agrees closely with the theoretical value. These results are in close agreement with the previous measurements of Edwards and Boehm. The present valjie_for_a|^ for the 501-keV transition agrees closely with the theoretical for an E3 multipolarity. From the 1 CC X-ray and gamma-ray relative intensities of the transitions in Gd and the previous measurement of the ratio of K conversion electrons for the 86- and 105-keV transitions of Subba Rao, it was possible to determine the K V conversion coefficients for the 86- and 105-keV transitions of «j, = 0.43 ±0.06 and = 0.23±0.03. These results are in agreement with the theo­ retical values for pure El transitions. The relative intensities of the 246-, 142- and 104-keV gamma rays following the decay of 22 minute were determined with improved precision in order that they might be used to determine accurately the conversion coefficients for these transitions. 1 I. INTRODUCTION A. Definition of the Internal Conversion Process Below 1-MeV the principal processes by which an excited nucleus can make a transition to a lower energy level are gamma-ray emission and inter­ nal conversion. In the first process the nucleus emits a gamma ray with energy equal to the transition energy, N*->-N+Y where N* is the nucleus in the excited state, N is the nucleus in the lower energy state and y is the emitted gamma ray which has an energy equal to the transition energy. In internal conversion the nuclear transition energy is transferred to one of the orbital electrons by a direct interaction be­ tween the electron and the charged nucléons. The electron is then ejected from the atom with an energy equal to the nuclear transition energy minus the binding energy of the electron. N*+Ze - N+(Z-l)e + e continuum ~ ^N*-N " ^binding where N* +Ze is the excited nucleus with Z electrons, N + (Z-l)e is the nucleus in the lower energy state with Z-1 electrons, is the ejected electron in the continuum, is the energy of the ejected electron, E^*_^ is the transition energy and is the binding energy of the ejected electron. Following the ejection of an internal conversion electron, the atomic electrons will readjust, and an outer electron will fill the vacancy. The energy difference is carried off by one of two processes. The first and predominant process is the emission of an X-ray which will have an energy equal to the difference between the binding energy of the shell in which the vacancy occurred and the binding energy of the shell from which the outer electron came. The other process by which energy is carried off following internal conversion is the emission of a second electron called an Auger electron. The resulting atom is ionized in two shells. The energy of the emitted electron is approximately given by E (KXY) = E (K) - E (X) - E^ (Y) = E (K) - E^ (X) - E (Y), where K, X, and Y are respectively the shell from which the internal conver­ sion electron is ejected, the shell from which the K shell is filled, and the shell from which the Auger electron is emitted. E^ (Y) is the electron binding energy of the Y shell in an atom with charge Z ionized in the X shell. For a given transition the internal conversion coefficient, a, is de­ fined as the ratio of N^, the number of internal conversion electrons emitted per unit time, to N^, the number of gamma rays emitted per unit time, " = lit • The internal conversion coefficient for a particular shell or subshell is defined similarly. For the K shell n5 3 |/ where is the number of internal conversion electrons emitted from the K shell per unit time. The total internal conversion coefficient is the sum of the internal conversion coefficients of the individual shells. B. Remarks About Internal Conversion Coefficients The internal conversion coefficients depend strongly on five para­ meters; the shell in which the conversion occurs, the transition energy, the atomic number, the angular momentum change and the parity change between the initial and final nuclear states. Internal conversion coefficients always increase as the transition energy decreases. They normally increase with Z, and always increase as the angular momentum, L, increases. To a large ex­ tent, internal conversion coefficients are independent of detailed nuclear structure. This makes it possible to obtain information about the spin and parity of the nuclear transition by comparing the experimentally determined conversion coefficients with those theoretically predicted. When the nuclear angular momenta for initial and final states are and J^, the emitted gamma ray can have any angular momentum L for which AJ = . The electromagnetic transitions are classified as electric 2^, EL, or mag­ netic 2^, ML, if the parity change between the initial and final nuclear states is (-1)'" or (-1)'"^^, respectively. The internal conversion coefficient is in general a mixture of 4 conversion coefficients of pure angular momentum L a = I ' where % a, =1. L ^ The aj^ represent the fraction of total gamma rays emitted with angular mo­ mentum L. For a given type of multipole, the relative intensity for multi- poles with L and L+2 is given by (1) ' - 1.
Load more

Recommended publications
  • Chapter 3 the Fundamentals of Nuclear Physics Outline Natural
    Outline Chapter 3 The Fundamentals of Nuclear • Terms: activity, half life, average life • Nuclear disintegration schemes Physics • Parent-daughter relationships Radiation Dosimetry I • Activation of isotopes Text: H.E Johns and J.R. Cunningham, The physics of radiology, 4th ed. http://www.utoledo.edu/med/depts/radther Natural radioactivity Activity • Activity – number of disintegrations per unit time; • Particles inside a nucleus are in constant motion; directly proportional to the number of atoms can escape if acquire enough energy present • Most lighter atoms with Z<82 (lead) have at least N Average one stable isotope t / ta A N N0e lifetime • All atoms with Z > 82 are radioactive and t disintegrate until a stable isotope is formed ta= 1.44 th • Artificial radioactivity: nucleus can be made A N e0.693t / th A 2t / th unstable upon bombardment with neutrons, high 0 0 Half-life energy protons, etc. • Units: Bq = 1/s, Ci=3.7x 1010 Bq Activity Activity Emitted radiation 1 Example 1 Example 1A • A prostate implant has a half-life of 17 days. • A prostate implant has a half-life of 17 days. If the What percent of the dose is delivered in the first initial dose rate is 10cGy/h, what is the total dose day? N N delivered? t /th t 2 or e Dtotal D0tavg N0 N0 A. 0.5 A. 9 0.693t 0.693t B. 2 t /th 1/17 t 2 2 0.96 B. 29 D D e th dt D h e th C. 4 total 0 0 0.693 0.693t /th 0.6931/17 C.
    [Show full text]
  • Cooperative Internal Conversion Process by Proton Exchange
    Cooperative internal conversion process by proton exchange P´eter K´alm´an∗ and Tam´as Keszthelyi† Budapest University of Technology and Economics, Institute of Physics, Budafoki ´ut 8. F., H-1521 Budapest, Hungary A generalization of the recently discovered cooperative internal conversion process is investigated theoretically. In the cooperative internal conversion process by proton exchange investigated the coupling of bound-free electron and proton transitions due to the dipole term of their Coulomb interaction permits cooperation of two nuclei leading to proton exchange and an electron emission. General expression of the cross section of the process obtained in the one particle spherical nuclear shell model is presented. As a numerical example the cooperative internal conversion process by proton exchange in Al is dealt with. As a further generalization, cooperative internal conversion process by heavy charged particle exchange and as an example of it the cooperative internal con- version process by triton exchange is discussed. The process is also connected to the field of nuclear waste disposal. PACS numbers: 23.20.Nx, 25.90.+k, 28.41.Kw, Keywords: internal conversion and extranuclear effects, other topics of nuclear reactions: specific reactions, radioactive wastes, waste disposal In a recent paper [1] a new phenomenon, the coop- erative internal conversion process (CICP) is discussed which is a special type of the well known internal conver- sion process [2]. In CICP two nuclei cooperate by neutron exchange creating final nuclei of energy lower than the en- ergy of the initial nuclei. The process is initiated by the coupling of bound-free electron and neutron transitions due to the dipole term of their Coulomb interaction in the initial atom leading to the creation of a virtual free neutron which is captured through strong interaction by an other nucleus.
    [Show full text]
  • Hadronic Physics II
    Geant4 10.1 p01 Hadronic Physics II Geant4 Tutorial at M&C+SNA+MC2015 19 April 2015 Dennis Wright (SLAC) Outline • Low energy hadronic models • Capture, Stopping and Fission • Gamma- and lepto-nuclear models • RadioacQve decay 2 Low Energy Neutron Physics • Below 20 MeV incident energy, Geant4 provides several models for treang neutron interacQons in detail • The high precision models (NeutronHP) are data-driven and depend on a large database of cross secQons, etc. • the G4NDL database is available for download from the Geant4 web site • elasQc, inelasQc, capture and fission models all use this isotope- dependent data • There are also models to handle thermal scaering from chemically bound atoms 3 Geant4 Neutron Data Library (G4NDL) • Contains the data files for the high precision neutron models • includes both cross secQons and final states • From Geant4 9.5 onward, G4NDL is based solely on the ENDF/B-VII database • G4NDL data is now taken only from ENDF/B-VII, but sQll has G4NDL format • use G4NDL 4.0 or later • Prior to G4 9.5 G4NDL selected data from 9 different databases, each with its own format • Brond-2.1, CENDL2.2, EFF-3, ENDF/B-VI, FENDL/E2.0, JEF2.2, JENDL-FF, JENDL-3 and MENDL-2 • G4NDL also had its own (undocumented) format 4 G4NeutronHPElasQc • Handles elasQc scaering of neutrons by sampling differenQal cross secQon data • interpolates between points in the cross secQon tables as a funcon of energy • also interpolates between Legendre polynomial coefficients to get the angular distribuQon as a funcQon of energy • scaered neutron and recoil nucleus generated as final state • Note that because look-up tables are based on binned data, there will always be a small energy non-conservaon • true for inelasQc, capture and fission processes as well 5 G4NeutronHPInelasQc • Currently supports 34 inelasQc final states + n gamma (discrete and conQnuum) • n (A,Z) -> (A-1, Z-1) n p • n (A,Z) -> (A-3, Z) n n n n • n (A,Z) -> (A-4, Z-2) d t • …….
    [Show full text]
  • Measurements of Some Internal Conversion Coefficients Using Scintillation Counter, Coincidence Techniques Ronald S
    Ames Laboratory Technical Reports Ames Laboratory 2-1964 Measurements of some internal conversion coefficients using scintillation counter, coincidence techniques Ronald S. Dingus Iowa State University W. L. Talbert Jr. Iowa State University E. N. Hatch Iowa State University Follow this and additional works at: http://lib.dr.iastate.edu/ameslab_isreports Part of the Physics Commons Recommended Citation Dingus, Ronald S.; Talbert, W. L. Jr.; and Hatch, E. N., "Measurements of some internal conversion coefficients using scintillation counter, coincidence techniques" (1964). Ames Laboratory Technical Reports. 85. http://lib.dr.iastate.edu/ameslab_isreports/85 This Report is brought to you for free and open access by the Ames Laboratory at Iowa State University Digital Repository. It has been accepted for inclusion in Ames Laboratory Technical Reports by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Measurements of some internal conversion coefficients using scintillation counter, coincidence techniques Abstract Internal conversion coefficients were measured by observing with a well-type Nal(Tl) crystal the photon spectra emitted during the de-excitation from the first excited state to the ground state of Gdl54,D)y 160, Ybl70, Ybl71 and Prl41 following the respective beta decays of Eul54, Tbl60, Tm170, Tml71 and Cel41. The results were obtained by analysis of either the singles spectra, or spectra obtained by coincidence-sum techniques, or both. For the coincidence work gating was done either with high energy gamma rays or with beta particles. The spectra from the Yb isotopes were analyzed on a computer using a least-squares curve- fitting program.
    [Show full text]
  • M1+E2) Mixed Character of the 9.2 Kev Transition in 227Th and Its Consequence for Spin-Interpretation of Low-Lying Levels
    Experimental evidence of (M1+E2) mixed character of the 9.2 keV transition in 227Th and its consequence for spin-interpretation of low-lying levels A. Kovalík a,b, А.Kh. Inoyatov a,c, L.L. Perevoshchikov a, M. Ryšavý b, D.V. Filosofov a, P. Alexa d, J. Kvasil e a Dzhelepov Laboratory of Nuclear Problems, JINR, 141980 Dubna, Moscow Region, Russian Federation b Nuclear Physics Institute of the ASCR, CZ-25068 Řež near Prague, Czech Republic c Institute of Applied Physics, National University, University Str. 4, 100174 Tashkent, Republic of Uzbekistan d Department of Physics, VSB-Technical University of Ostrava, 17. listopadu 2172/15, 708 00 Ostrava, Czech Republic e Institute of Particle and Nuclear Physics, Charles University, CZ-18000, Praha 8, Czech Republic Keywords: Internal conversion electron spectroscopy; Nuclear transition; Transition multipolarity; Spin-Parity; 227Ac; 227Th The 9.2 keV nuclear transition in 227Th populated in the -decay of 227Ac was studied by means of the internal conversion electron spectroscopy. Its multipolarity was proved to be of mixed character M1+E2 and the spectroscopic admixture parameter δ2(E2/M1)=0.695±0.248 (|δ(E2/M1)| =0.834±0.210) was determined. Nonzero value of δ(E2/M1) raises a question about the existing theoretical interpretation of low-lying levels of 227Th. 1. Introduction The interpretation of the level structure of 227Th is still a major problem mainly due to the lack of experimental information on the low-lying levels of 227Th and a long-standing controversy [1] about the spin-parity of the 227Th ground state, which represents the basis for all other level spin- parity assignments.
    [Show full text]
  • What Is Internal Conversion? Our Measurement Impurity Corrections
    Precise Measurement of !T for the 39.76-keV E3 Transition in 103Rh A Further Test of Internal Conversion Theory Vivian Sabla1,2, N. Nica2, and J.C. Hardy2 1 Middlebury College, Middlebury, VT 05753 2 Cyclotron Institute, Texas A&M University, College Station, TX 77840 Theory - What is Internal Conversion? Our Measurement Impurity Corrections Internal Conversion is a process that occurs when an • 103 excited atom decays. When the atom decays, either a "-ray is We activated a source of Pd through thermal neutron • We fit the peaks of the "-rays, x-rays and impurities using the emitted or the energy from the nucleus is transferred to an inner- activation in the TRIGA reactor at Texas A&M University gf3 program in the Radware package. orbital electron, knocking the electron from the atom. Internal • 103Pd decays through electronic capture to 103Rh with a half-life • 111Ag impurity contributed to our x-ray package. We were able conversion is this process of transferring energy to an electron. of 16.991 days. to correct for the x-ray impurity using: When the inner-orbital electron is bumped out of the atom, a • Source “cooled down” for three weeks before we began our higher energy electron jumps down to fill its place, emitting a A(342γ) gamma spectroscopy allowing for short-lived radioactive A(Cd Kx)= ✏ph(23.6keV ) I(23.6keV ) characteristic x-ray in the process. impurities to decay away ✏ph(342γ) I(342γ) ⇥ ⇥ The ratio of the probability of internal conversion to the ⇥ probability of "-emission is called the Internal Conversion • Decay spectra were taken using our precisely efficiency • Our 40-keV gamma peak was confirmed to be the product of calibrated HPGe Detector.
    [Show full text]
  • Theory of Nuclear Excitation by Electron Capture for Heavy Ions
    Theory of nuclear excitation by electron capture for heavy ions Inaugural Dissertation zur Erlangung des Doktorgrades der Naturwissenschaften der Justus-Liebig-Universit¨at Gießen Fachbereich 07 vorgelegt von Adriana Gagyi-P´alffy aus Bukarest, Rum¨anien Gießen 2006 Dekan: Prof. Dr. Volker Metag 1. Berichterstatter: Prof. Dr. Werner Scheid 2. Berichterstatter: Prof. Dr. Alfred Muller¨ Tag der mundlic¨ hen Prufung:¨ Contents Introduction 5 Aim and motivation of this thesis . 6 Contents of this thesis . 7 1 Theory of electron recombination 9 1.1 Decomposition of the Fock space . 11 1.2 The total Hamiltonian of the system . 12 1.3 Expansion of the transition operator . 14 1.4 Total cross section for NEEC . 18 2 Theory of NEEC 21 2.1 Nuclear model . 21 2.2 NEEC rates for electric transitions . 27 2.3 NEEC rates for magnetic transitions . 29 3 Total cross sections for NEEC 31 3.1 Numerical results . 31 3.2 Possible experimental observation of NEEC . 37 3.2.1 Electron Beam Ion Traps . 37 3.2.2 Ion Accelerators . 40 4 Interference between NEEC and RR 45 4.1 Interference term in the total cross section . 45 4.2 Electric transitions . 50 4.3 Magnetic transitions . 52 4.4 Numerical results . 54 5 Angular distribution of emitted radiation 59 5.1 Alignment of the excited nuclear state . 60 5.2 Radiative decay of the excited nuclear state . 62 5.3 Numerical results . 65 Summary and Outlook 73 Summary . 73 Outlook . 74 Deutschsprachige Zusammenfassung 77 3 CONTENTS Appendix A The magnetic Hamiltonian 81 B Magnetic transitions in the nuclear collective model 85 C Calculation of matrix elements involving spherical tensors 89 Bibliography 95 Acknowledgments 107 4 Introduction When Niels Bohr proposed in 1913 his first model of the atom, he depicted it as having a small and dense positively charged nucleus, surrounded by the orbiting electrons.
    [Show full text]
  • Introduction to Nuclear Physics and Nuclear Decay
    NM Basic Sci.Intro.Nucl.Phys. 06/09/2011 Introduction to Nuclear Physics and Nuclear Decay Larry MacDonald [email protected] Nuclear Medicine Basic Science Lectures September 6, 2011 Atoms Nucleus: ~10-14 m diameter ~1017 kg/m3 Electron clouds: ~10-10 m diameter (= size of atom) water molecule: ~10-10 m diameter ~103 kg/m3 Nucleons (protons and neutrons) are ~10,000 times smaller than the atom, and ~1800 times more massive than electrons. (electron size < 10-22 m (only an upper limit can be estimated)) Nuclear and atomic units of length 10-15 = femtometer (fm) 10-10 = angstrom (Å) Molecules mostly empty space ~ one trillionth of volume occupied by mass Water Hecht, Physics, 1994 (wikipedia) [email protected] 2 [email protected] 1 NM Basic Sci.Intro.Nucl.Phys. 06/09/2011 Mass and Energy Units and Mass-Energy Equivalence Mass atomic mass unit, u (or amu): mass of 12C ≡ 12.0000 u = 19.9265 x 10-27 kg Energy Electron volt, eV ≡ kinetic energy attained by an electron accelerated through 1.0 volt 1 eV ≡ (1.6 x10-19 Coulomb)*(1.0 volt) = 1.6 x10-19 J 2 E = mc c = 3 x 108 m/s speed of light -27 2 mass of proton, mp = 1.6724x10 kg = 1.007276 u = 938.3 MeV/c -27 2 mass of neutron, mn = 1.6747x10 kg = 1.008655 u = 939.6 MeV/c -31 2 mass of electron, me = 9.108x10 kg = 0.000548 u = 0.511 MeV/c [email protected] 3 Elements Named for their number of protons X = element symbol Z (atomic number) = number of protons in nucleus N = number of neutrons in nucleus A A A A (atomic mass number) = Z + N Z X N Z X X [A is different than, but approximately equal to the atomic weight of an atom in amu] Examples; oxygen, lead A Electrically neural atom, Z X N has Z electrons in its 16 208 atomic orbit.
    [Show full text]
  • Formation of Helium of Mass 3 in an Excited State
    No. 3625, APRIL 22, 1939 NATURE 681 Radio bromine which were projected in the forward direction (0-10°). Don C. De Vault and W. F. Libby1 and E. Segre, Three series of experiments were made. In the first R. S. Halford and G. T. Seaborg• have shown that experiment methane was used in the cloud chamber the 4·5-hr. radiobromine transforms into the 18-min. and the neutrons were observed at 90° to the direction isotope which is [3-active, by the emission of softy-rays. of the 0·9 Mv. deutrons. In the second experiment Le Roux, Lu and Sugden3 find that this is the method the conditions were the same except that helium was of disintegration of at least 90 per cent of 4 ·5-hr. used in the cloud chamber. In the third experiment radiobromine. Segre, Halford and Seaborg2 predicted the neutrons were observed at an angle of oo to the that the y-rays would be soft, and a large proportion 0·5 Mv. deuterons. A summary of the results is would be internally converted. given in the accompanying table. These considerations are in agreement with observations made in a Wilson chamber of the dis­ c:,: I Relative Relative integration of 4·5-hr. radiobromine. Measurement of - o ;a I intensity intensity tracks starting from thin foils which had been activated with radiobromine, and from active ethyl ., .,... ation (Mv.) ------------- A low high low high bromide introduced as a vapour into the chamber, ___ __! energy energy energy energy show homogeneous energy groups of electrons due H 0·90 190°±8° 11·5 · 2·81 0·28 1·00 0·17 to the K and L conversion of this y-ray, superimposed He I 0·90 90°±15° 1·5 ; 3·0 0·92 1·00 0·1-{}·2 1·00 on a background of the continuous [3-ray spectrum H 0·50 0°±9° 1·93;3·55 0·19 1·00 0·12 1·00 of the [3-active isotope.
    [Show full text]
  • Enhancement Mechanisms of Low Energy Nuclear Reactions
    Enhancement Mechanisms of Low Energy Nuclear Reactions Gareev F.A., Zhidkova I.E. Joint Institute for Nuclear Research, 141980, Dubna, Russia [email protected] [email protected] 1 Introduction One of the fundamental presentations of nuclear physics since the very early days of its study has been the common assumption that the radioactive process (the half-life or decay constant) is independent of external conditions. Rutherford, Chadwick and Ellis [1] came to the conclusion that: • ≪the value of λ (the decay constant) for any substance is a characteristic constant inde- pendent of all physical and chemical conditions≫. This very important conclusion (still playing a negative role in cold fusion phenomenon) is based on the common expectation (P. Curie suggested that the decay constant is the etalon of time) and observation that the radioactivity is a nuclear phenomenon since all our actions affect only states of the atom but do not change the nucleus states. We cannot hope to mention even a small part of the work done to establish the constancy of nuclear decay rates. For example, Emery G.T. stated [2]: • ≪Early workers tried to change the decay constants of various members of the natural radioactive series by varying the temperature between 24◦K and 1280◦K, by applying pressure of up to 2000 atm, by taking sources down into mines and up to the Jungfraujoch, by applying magnetic fields of up to 83,000 Gauss, by whirling sources in centrifuges, and by many other ingenious techniques. Occasional positive results were usually understood, arXiv:nucl-th/0505021v1 8 May 2005 in time, as result of changes in the counting geometry, or of the loss of volatile members of the natural decay chains.
    [Show full text]
  • Nuclear Structure Effects In
    NUCLEAR STRUCTURE EFFECTS IN INTERNAL CONVERSION Thesis by Edwin Charles Seltzer In Partial Fulfillment of the Requirements For the Degree of Doctor of Philosophy · California. I.nstitute of Technology. Pasadena, California 1966 (Submitted October 13, 1965) ii ACKNOWLEDGEMENTS The author would like to thank: Professor F. Boehm, for his interest and support. Dr. E. Kankeleit, for his time and interest in the completion of this thesis. R. Hager, who collaborated with the author in all phases of a program of investigating internal conversion effects. H. Hendrickson and R. Marcley for their support in problems involving experimental equipment. Dr. R •. Brockmeier, for many discussions concerning programming for digital computers. iii ABSTRACT Experimental studies of nuclear effects in internal conversion 181 175 in Ta and Lu have been performed. Nuclear structure effects ("penetration" effects), in internal conversion are described in general. Calculations of theoretical conversion coefficients are out- lined. Comparisons with the theoretical conversion coefficient tables of Rose and Sliv and Band are made. Discrepancies between our results and those of Rose and Sliv are noted. The theoretical conversion coefficients of Sliv and Band are in substantially better agreement with our results than are those of Rose. The ratio of the Ml pene- tration matrix element to the Ml ganuna-ray matrix element, cal­ 181 led~, is equal to+ 175 ± 25 for the 482 keV transition in Ta • 175 The results for the 343 keV transition in Lu indicate that ~ may be as large as - 8 ± 5. These transitions are discussed in terms of the unified collective model. Precision L subshell measurements in 169 182 181 Tm (130 keV)~ w (iOO keV), and Ta (133 keV) show definite systematic deviations from the theoretical conversion coefficients.
    [Show full text]
  • 1 ,.,. the Origin Gamma Rays Doughs Re41i!J
    1 ,.,. The Origin of Gamma Rays Doughs Re41i!j 1.1 GAMMA RAYS AND THE EIECI’ROMAGNETIC sPEclmJM Gamma rays are high-energy electromagnetic radiation emitted in the deexcitation of the atomic nucleus. Electromagnetic radiation includes such diverse phenomena as radio, television, microwaves, infrared radation, light, ultraviolet radiation, x rays, and gamma rays. These ti]ations all propagate througli vacuum with the speed of light. They can be described as wave piienomena involving electric and magnetic field oscillations analogous to mechanical oscillations such as water waves or sound. They differ from each other only in the frequency of oscillation. Although given dWferent names, electromagnetic radiation actually forms a continuous spect~m, from low- frequency radio’ waves at a few cycles per second to gamma rays at 1018 Hz and above (see Figure 1.1). The parameters used to describe’ an electromagnetic wave— fre@ency, wavelength, and energy—are related and maybe used interchangeably. It is common practice to use frequency or wavelength for radio’waves, color or wavelength for light waves (including infrared and ultraviolet), and energy for x rays and gamma rays. Frequenty Wavelength Energy (Hz) (meters)(electronvolts) 1(i” Oamma Rays +-- 106 (1MeV) 1 i?’ x Rays id’ + 103 (1 keV) 10’8 ultraviolet 10-8 10’5 \\S Wsibb SSSSS 4-10° (1 eV) Inrrared 10-5 10’2 ehon mdlo waves 10-2 llf 10’ V \\\\\\\\\\\\\\~\\\\\\\ boadcasl emd t Mefmhertz lcf’ \\\\\\\\\\\\\\\\\\\\\\\\\\ 104 1 kit01wrt2 ltf LongRadio Waves 10’ lrf’ // Power Lines Fig. 1.1 The electromagnetic spectrum showing the relationship between gamma rays, x rays, light waves, and radio waves.
    [Show full text]